Reference Guide

Intermediate System to Intermediate System (IS-IS) | 819

Intermediate System to Intermediate System

(IS-IS)

Overview

Intermediate System to Intermediate System Protocol (IS-IS) for IPv4 and IPv6is supported only on

the E-Series platform, as indicated by the e character under each command heading.

IS-IS is an interior gateway protocol that uses a shortest-path-first algorithm. IS-IS facilitates the

communication between open systems, supporting routers passing both IP and OSI traffic.

A router is considered an intermediate system. Networks are partitioned into manageable routing

domains, called areas. Intermediate systems send, receive, and forward packets to other routers within

their area (Level 1 and Level 1-2 devices). Only Level 1-2 and Level 2 devices communicate with

other areas.

IS-IS protocol standards are listed in the Standard Compliance chapter in the FTOS Configuration

Guide.

Commands

The following are the FTOS commands to enable IS-IS.

• adjacency-check

• advertise

• area-password

• clear config

• clear isis

• clns host

• debug isis

• debug isis adj-packets

• debug isis local-updates

• debug isis snp-packets

• debug isis spf-triggers

• debug isis update-packets

Note: The fundamental mechanisms of IS-IS are the same between IPv4 and IPv6. Where

there are differences between the two versions, they are identified and clarified in this chapter.

Except where identified, the information in this chapter applies to both protocol versions.